Light and heat sensitive system comprising a leuco base of a dialkylamino polyarylmethane dye quaternized to the maximum extent

ABSTRACT

THE LEUCO BASE OF A POLYARYLMETHANE DYE, SUCH AS CYRSTAL VIOLET OR MALACHITE GREEN, WHICH HAS BEEN QUATERNIZED TO THE MAXIMUM EXTENT WITH AN ALKYL IODIDE, SUCH AS METHYL IODIDE, IS A RADIATION-SENSITIVE MATERIAL WHICH IS USEFUL IN THE PREPARATION OF IMAGES BY THERMOGRAPHIC AND PHOTOTHERMOGRAPHIC PROCESSES. IMAGES IN A VARIETY OF COLORS CAN BE PREPARED FROM ELEMENTS CONTAINING THIS MATERIAL BY IMAGEWISE EXPOSURE TO HEAT OR BY IMAGEWISE EXPOSURE TO ULTRAVIOLET RADIATION OR HALOGEN VAPOR, PRECEDED OR FOLLOWED BY UNIFORM EXPOSURE TO HEAT.

United States Patent 3,592,650 LIGHT AND HEAT SENSITIVE SYSTEM COMPRIS- ING A LEUCO BASE OF A DIALKYLAMINO POLYARYLMETHANE DYE QUATERNIZED TO THE MAXIMUM EXTENT Roy C. De Selms, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y. No Drawing. Filed Aug. 1, 1969, Ser. No. 846,964 Int. Cl. G01n 21/34; G03c 5/24 US. CI. 96-48 22 Claims ABSTRACT OF THE DISCLOSURE The leuco base of a polyarylmethane dye, such as crystal violet or malachite green, which has been quaternized to the maximum extent with an alkyl iodide, such as methyl iodide, is a radiation-sensitive material which is useful in the preparation of images by thermographic and photothermographic processes. Images in a variety of colors can be prepared from elements containing this material by imagewise exposure to heat or by imagewise exposure to ultraviolet radiation or halogen vapor, preceded or followed by uniform exposure to heat.

This invention relates to image reproduction. In a particular aspect it relates to thermosensitive and photothermosensitive elements containing polyarylmethane dyes and to processes of reproducing images with such ele ments.

Triarylmethane dyes have been previously used in photographic and thermographic reproduction. Sprague et al. in US. Pat. 2,940,866 described a heat-sensitive copying sheet which has a heat-sensitive layer comprising a colorless carbinol base of a triphenylmethane dye and an acid former. Upon exposure to heat the colored dye is formed. Fichter et al. in US. Pat. 3,102,029, described a photosensitive print-out composition which comprises an organic halogen compound, an aryl amine, and the carbinol base of a diphenylmethane or triphenylrnethane dye as a sensitizer. In photoexposed areas a colored dye image is formed. Sprague et al. in US. Pat. 3,121,632 described a photosensitive composition which comprises the leuco base of a triphenylmethane dye and an activator therefor, which is an organic compound containing a carbonyl group. Photoexposure converts the leuco base to the colored dye form.

In all of these prior art systems the formation of an image depends upon the interaction between two components. I have found that stable images can be prepared using a quaternized leuco base of certain triarylmethane dyes as the sole radiation-sensitive component of the radiation-sensitive element.

It is an object of this invention to provide novel radiation-sensitive compositions and elements containing a quaternized leuco base of a triarylmethane dye.

It is another object of this invention to provide a thermorgraphic process for the reproduction of images with elements utilizing a quaternized leuco base of a triarylmethane dye as the sole radiation-sensitive component.

It is yet another object of this invention to provide a photothermographic process for reproduction of images with elements employing as the sole radiation-sensitive component a quaternized leuco base of a triarylmethane dye.

The above and other objects of this invention will become apparent from the further description of the invention which follows.

In accordance with the present invention, there is provided a radiation-sensitive element which comprises a support and a leuco base of a polyarylmethane dye containing at least one dialkylamino group and which has been quaternized to the maximum extent with an alkyl 3,592,650 Patented July 13, 1971 iodide. The quaternized leuco bases are thermosensitive and upon heating to a temperature of at least about C., a color change occurs in heated areas. By appropriate selection of the quaternized leuco base of the polyarylmethane dye, images in a wide variety of colors can be prepared. In addition to being thermosensitive, the quaternized leuco bases are sensitive to both ultraviolet radiation and halogen vapor, and when elements containing them are exposed to ultraviolet radiation or halogen vapor, a latent image is formed which can be developed by heating to a temperature of at least about 150 C. Alternatively, uniform heating can precede exposure to ultraviolet radiation or halogen vapor, and then exposure is sufficient to form a visible print-out image in the element.

The leuco bases of dialkylamino polyarylmethane dye which are quaternized with an alkyl iodide to form radiation sensitive compounds useful in this invention include leuco bases of dialkylamino diarylmethane dyes and leuco bases of dialkylamino triarylmethane dyes such as crystal violet leuco base, malachite green leuco base, u,u-bis(pdimethylaminophenyl)-p-cresol, 4,4-methylene-bis(N,N- dimethylaniline), and the like. Triarylmethane dyes are preferred.

Typical of quaternized leuco bases of the preferred dialkylamino triarylmethane dyes are those which can be represented by the structural formula:

wherein each R is independently a hydrogen atom, a halogen atom, a hydroxy group, a cyano group, an alkyl group generally having one to eight carbon atoms, e.g., methyl, ethyl, propyl, butyl, amyl, hexyl, heptyl, octyl, etc., or an alkoxy group generally having one to eight carbon atoms, e.g., methoxy, ethoxy, propoxy, butoxy, amyloxy, hexoxy, heptoxy, octyloxy, etc.; each R is independently an R group or a 1 G9 l1\TR4X group at least one of the R groups being a 1| ea -III--R4XG9 group R is an alkyl group generally having one to four carbon atoms; R, is an alkyl group generally having one to eight carbon atoms; X is an iodide ion.

These quaternized leuco bases can be prepared by refluxing a leuco base having the structural formula:

3 with an alkyl halide having the structural formula: R X, wherein R R R and X are as defined above and R is an R group or a group Shortly after being dissolved in certain solvents, the quaternized leuco bases precipitate as a solvate. This has been found to be a convenient method for purifying the quaternized leuco base. Solvents with which this effect is observed include alkanols such as methanol, ethanol, etc., and nitriles such as acetonitrile, propionitrile, etc. The solvated quaternized leuco bases are radiation sensitive and can be used in this invention in the same manner as the unsolvated quaternized leuco base.

Photosensitive elements can be prepared by coating a quaternized leuco base of a dialkylamino polyarylmethane dye on a support either with or without a binder or by imbibing the leuco base into a suitable porous support. Suitable supports include fiber base materials such as paper, polyethylene-coated paper, glassine, 'vegetable parchment, ceramic materials, glass, sheets and foils of such metals as aluminum, copper, steel, etc., polymeric film base such as polystyrene film base, cellulose acetate film base, cellulose nitrate film base, poly(ethylene terephthalate) film base, poly(ethylene sebacate) film base and polymeric film base on which is coated such porous materials as gelatin, olefinic polymers, such as polyvinyl alcohol, etc., and the like.

Suitable binders with which the quaternized leuco bases can be mixed and coated on a support include gelatin, polyvinyl alcohol, polyvinyl chloride, polyvinyl acetate, hydroxymethyl cellulose, hydroxyethyl cellulose, and the like.

in accordance with one embodiment of this invention the radiation-sensitive element is exposed to heat to effect a color change and produce an image in heated areas. This can be accomplished by heating the element in an imagewise manner, for example, by contacting it with heated needles, hot metal type and other heated images, or it can be effected by contacting the element with an infrared absorbing image and exposing the element in contact with the image to a source of infrared radiation. A temperature in the vicinity of the melting point of the quaternized leuco base generally is required to effect the color change. With most of the compounds of this invention temperatures of at least about 150 C. are required and temperatures of between 150 C. and 200 C. are preferred. At temperatures much above 200 C., many supports begin to char. By appropriate choice of substituents on the aryl nucleus the temperature at which a color change will occur may be lowered below 0 C.

'In accordance with a second embodiment of this invention, the radiation-sensitive element is imagewise exposed to ultraviolet and is heated overall to a temperature of at least about 150 C. to effect a color change in exposed areas. These two steps can occur in either order. For example, the element can be imagewise exposed to ultraviolet radiation to form a latent image and then the latent image can be developed by uniformly heating the element to a temperature of at least about 150 C. Alternatively, the element can be uniformly heated to a temperature of at least about 150 C. so that the faintest trace of color appears on the element, after which the element is imagewise exposed to ultraviolet radiation and a print-out image will be obtained in exposed areas of the element. It has been observed that a trialkylamine is released upon ultraviolet exposure of the quaternized leuco base.

Alternatively, in lieu of the use of ultraviolet radiation, this second embodiment of the invention can be effected with a halogen vapor such as bromine vapor, chlorine vapor or iodine vapor. The halogen vapor can be provided directly, or with a halogen generating compound such as sulfuryl chloride. The element can be imagewise exposed to a halogen vapor through a mask, or by the use of jets of halogen vapor.

Since the element used in this embodiment of the invention is heat sensitive, the same as the element in the preceding embodiment of the invention, care must be observed during the uniform exposure of the element to heat that the-colored dye does not form in non-image areas of the element. Thus, when the element is uniformly exposed to heat prior to imagewise exposure to ultraviolet radiation or iodine vapor, heat should be removed before any significant color develops in the element. Otherwise, discrimination between image and nonimage areas will be reduced. Similarly, when the element is uniformly exposed to heat subsequent to imagewise exposure to ultraviolet radiation or iodine vapor, the heat should be removed as soon as an image of adequate density develops. This will reduce the possibility of fog developing in non-image areas.

The following examples further illustrate the practice of the invention.

EXAMPLE 1 Leuco crystal violet trismethiodide A mixture of 18.7 g. (0.05 mole) of leuco crystal violet and 25 ml. (57 g., 0.40 mole) of methyl iodide is heated at reflux for 30 minutes and the excess methyl iodide evaporated at reduced pressure leaving 40 g. of crude, colorless product, M.P. 180-190 C. (turning intense blue). The NMR spectrum is consistent with the proposed structure.

Analysis.Calcd. for C H N I (percent): C, 42.1; H,5.0; N, 5.3; I, 47.6. Found (percent): C, 39.6; H, 4.8; N, 5.0; I, 44.2.

'EXAMPLE 2 The monomethanolate of leuco crystal violet trismethiodide The trismethiodide of leuco crystal violet (Example 1, 10 g.) is stirred with ml. of absolute methanol for 30 minutes, during which time it dissolves and reprecipitates as the solvate. The colorless solid, 5.85 g., is collected by filtration, M.P. 184-5 C. (turning intense blue). The NMR spectrum indicates that this is the monomethanolate.

Analysis.-Calcd. for C H N I -CH OH (percent): C, 41.9; H, 5.3; N, 5.1; I, 45.8. Found (percent): C, 40.6; H, 4.8; N, 4.9; I, 45.1.

EXAMPLE 3 The bisethanolate of leuco crystal violet trismethidodide The procedure of Example 2 is followed substituting absolute ethanol for the methanol. There is obtained 8.3 g. of colorless solid product. The NMR spectrum indicates 2 moles of ethanol of solvation.

Analysis.-Calcd. for C H N I -2C H OH (percent): C, 43.1; H, 5.9; N, 4.7; I, 42.7. Found (percent): C, 40.4; H, 5.0; N, 4.7; I, 42.8.

EXAMPLE 4 The monoacetonitrileate of leuco crystal violet trismethiodide The procedure of Example 2 is followed substituting acetonitrile for the methanol. There is obtained 9.3 g. of colorless solid product. The NMR spectrum indicates 1 mole of acetonitrile of solvation.

Analysis.-Calcd. for C H N I -CH CN (percent): C, 42.9; H, 5.2; N, 6.7; I, 45.3. Found (percent): C, 42.5; H, 5.1; N, 6.0; I, 45.4.

EXAMPLE Leuco malachite green bismethiodide monomethanolate filtered yielding 8.5 g. of colorless solid product, M.P. I

1946 C. (turning intense green).

Analysis.Calcd. for C H N I -CH OH (percent): C, 48.3; H, 5.6; N, 4.3; I, 39.3. Found (percent): C, 49.3 H, 5.2; N, 4.4; I, 39.5.

EXAMPLE 6 Thermographic system employing solvates of leuco crystal violet trismethiodide A solution containing approximately percent of leuco crystal violet trismethiodide prepared in Example 1 in a mixture (1:1) of methanol and acetonitrile is ap plied to filter paper. The solvent is allowed to evaporate. The color of the sensitive paper turns to pale yellow, but is otherwise uneifected by application of a solution of chloranil, heating at 4550 C. for 4 days at ambient room humidity, or standing at ambient room conditions for at least 1 /2 months. Upon heating by tflame, heat lamp, or hot plate (approximately 150-200 C.), an intense blue color develops in the heated area on the fresh and aged samples. When placed against an image and exposed to infrared radiation, the blue color develops in the vicinity of the dark image. The blue color is also stable to the above-mentioned incubation conditions.

EMMPLE 7 Thermographic system employing solvates of leuco malachite green bismethiodide A solution containing approximately 10 percent leuco malachite green bismethiodide monomethanolate prepared in Example 5 in (1:1) methanol and acetonitrile employed as in Example 6 gives results similar to Example 6, except in this case an intense green color appears upon heating.

EXAMPLE 8 Thermographic system employing 4,4-methylene-bis (N,N-dimethylaniline)bismethiodide To 25 ml. (57 g., 0.40 mole) of methyl iodide is added 12.7 g. (0.05 mole) of 4,4-methylene-bis(N,N-dimethylaniline), which initially goes into solution and then precipitates. The mixture is heated at reflux to evaporate the excess methyl iodide. A 10 percent solution of the crude 4,4 methylene-bis(N,N-dimethylaniline)bis-methiodide in a mixture (1:1) of methanol and acetonitrile is pre pared and applied to filter paper. When heated as in Example 6 a pale green image is obtained in those areas exposed to heat.

EXAMPLE 9 Photothermographic system employing solvates of leuco crystal violet trismethiodide A coated paper is prepared as described in Example 6, taking care that it is exposed to as little light as possible. The paper is then exposed through a pattern to a 275 watt General Electric Type RS Sunlamp at 4 inches distance for periods of 1 second to several minutes. The whole paper when subjected to heat greater than 150 C. causes development of a blue image in the previously irradiated areas. The latent image can be kept at least 3 days in the dark before heat development.

6 EXAMPLE 10 The same procedure as for Example 9 is followed, but iodine vapor is used in the place of ultraviolet light for exposure. Similar results are obtained.

EXAMPLE 11 A coated paper is prepared as described in Example 6. This paper is then heated at a temperature above C. until the faintest blue color develops. The paper so prepared is irradiated through a pattern for one to three minutes with a 275 watt General Electric Type RS Sunlamp at 4 inches distance. A dark blue image forms in the irradiated areas. This image is stable in the dark for at least two weeks at ambient temperatures.

EXAMPLE 12 The same procedure as for Example 11 is used. However, iodine vapor is used instead of ultraviolet light for exposure.

EXAMPLE l3 Photothermographic system employing solvates of leuco malachite green bismethiodide The element prepared in Example 7 is used in the process described in Example 9. A green image is obtained in irradiated areas.

EXAMPLE 14 Photothermographic system employing 4,4 methylenebis (N,N-dimethylaniline bismethiodide The element prepared in Example 8 is used in the process described in Example 9 to give a pale green image in irradiated areas of the element.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

What is claimed is:

1. A radiation-sensitive element which comprises a support and a radiation-sensitive material which is a leuco base of a dialkylamino polyarylmethane dye all the amino groups of which are quaternized with an alkyl iodide.

2. A radiation-sensitive element as defined in claim 1 wherein the radiation-sensitive material is carried in a film-forming binder.

3. A radiation-sensitive element as defined in claim 1 wherein the dialkylamino polyarylmethane dye is a dialkylamino triarylmethane dye.

4. A radiation-sensitive element as defined in claim 3 wherein the radiation-sensitive material has the structural formula:

wherein each R is independently selected from the group consisting of hydrogen atoms, halogen atoms, hydroxy groups, cyano groups, alkyl groups and alkoxy groups;

6 X group R and R are alkyl groups and X is an iodide ion.

5. A radiation-sensitive element as defined in claim 1 wherein the leuco base is selected from the group consisting of leuco crystal violet and leuco malachite green and the alkyl iodide is methyl iodide.

6. A radiation-sensitive element which comprises a support on which is coated leuco crystal violet trismethiodide.

7. A radiation-sensitive element which comprises a support on which is coated leuco malachite green bismethiodide.

8. A thermographic proces for preparation of images which compirses imagewise exposing to a temperature of at least about 150 C., a radiation-sensitive element which comprises a support and a radiation-sensitive material which is a leuco base of a. dialkylamino polyarylmethane dye all the amino groups of which are quaternized with an alkyl iodide to form an image in exposed areas of the element.

9. A thermographic process a defined in claim 8 wherein the dialkylamino polyarylmethane dye is a dialkylamino triarylmethane dye.

10. A thermographic process as defined in claim 9 wherein exposing the element to a temperature of at least about 150 C. is effected by contacting the element with a surface at a temperature of at least about 150 C.

11. A thermographic process as defined in claim 9 wherein exposing the element to a temperature of at least about 150 C. is effected by contacting the element with an infrared absorbing image and exposing the element and the image to infrared radiation for a time sufficient to heat areas in contact with the image to a temperateure of at least about 150 C.

12. A thermographic process as defined in claim 11 wherein the leuco base is selected from the group consisting of leuco crystal violet and leuco malachite green and the alkyl iodide is methyl iodide.

:13. A photothermographic process for preparation of images which comprises imagewise exposing to ultraviolet radiation an element which comprises a support and a radiation-sensitive material which is a leuco base of a dialkylamino polyarylmethane dye all the amino groups of which are quaternized with an alkyl iodide, and uniformly heating the element to form an image in exposed areas of the element.

14. A photothermographic process as defined in claim 13 wherein the dialkylamino polyarylmethane dye is a dialkylamino triarylmethane dye.

15. A photothermographic process as defined in claim 14 wherein uniform heating of the element is subsequent to imagewise exposure to ultraviolet radiation.

16. A photothermographic process as defined in claim 14 wherein uniform heating of the element precedes imagewise exposure to ultraviolet radiation.

17. A photothermographic process as defined in claim 15 wherein the radiation-sensitive material has the structural formula:

wherein each R is independently selected from the group consisting of hydrogen atoms, halogen atoms, hydroxy groups, cyano groups, alkyl groups and alkoxy groups; each R is independently selected from the group consisting of R groups and l a .QlTI-R; X groups at least one of the R groups being a 1?": ll -Ri X group R and R are alkyl groups and X is an iodide ion.

18. A photothermographic process as defined in claim 15 wherein the leuco base is selected from the group consisting of leuco crystal violet and leuco malachite green and the alkyl iodide is methyl iodide.

19. A thermographic process for preparation of images which comprises imagewise exposing to iodine vapor an element which comprises a support and a radiation-sensitive material which is a leuco base of a dialkylamino polyarylmethane dye all the amino groups of which are quaternized with an alkyl iodide, and uniformly heating the element.

20. A thermographic process as defined in claim 19 wherein the dialkylamino polyarylmethane dye is a dialkylamino triarylmethane dye.

21. A thermographic process as defined in claim 20 wherein uniform heating of the element is subsequent to imagewise exposure to iodine vapor.

22. A thermographic process as defined in claim 20 wherein uniform heating of the element precedes imagewise exposure to iodine vapor.

References Cited UNITED STATES PATENTS 2,839,542 6/1958 Chalkley 9690 2,940,866 6/1960 Sprague et a1. 11736.8 3,102,029 8/1963 Fichter 96-48 3,121,633 2/1964- Sprague et a1. 9648 NORMAN G. TORCHIN, Primary Examiner R. E. FIGHTER, Assistant Examiner US. Cl. X.R. 

